Recently, digital broadcasting has started in satellite broadcasting and terrestrial broadcasting. In the digital broadcasting, data such as compressed, encoded video data (picture data), audio data (sound data) and other management data corresponding to a plurality of channels are generally multiplexed for transmission. The video data and audio data are generally compressed and encoded according to the MPEG1 or MPEG2 method. An MPEG2 transport stream (TS: Transport Stream; hereinafter, simply referred to as “TS” as appropriate) is generally used for multiplexing. A standard for transmitting such a transport stream from a set-top box to another equipment through a digital interface such as IEEE1394 has also been determined.
FIG. 7 is a diagram showing a general structure of the transport stream. As shown in FIG. 7, a transport stream is formed from 188-byte packets (TS packets). Each TS packet is divided into a header portion and a data portion. The header portion includes reference time information called PCR (Program Clock Reference) and the like. On the other hand, the data portion includes one type of data out of general data such as video data, audio data, program specific information (PSI) data and additional data.
As shown in FIG. 7(a), a bitstream of the video data, audio data or additional data is called an elementary stream. The elementary stream is packetized by a prescribed unit into PES (Packetized Elementary Stream) packets. The PES packet is formed from a PES packet header and PES packet data that forms a part of the elementary stream. The PES packet header includes decoding time (DTS), display time (PTS) and the like of the elementary stream. The PES packet is packetized by a prescribed unit into TS packets each having a TS packet header added thereto.
On the other hand, as shown in FIG. 7(b), the program specific information data is called a PSI section. The PSI section is formed from a PSI section header and a PSI table. The PSI section is packetized by a prescribed unit into TS packets each having a TS packet header added thereto.
It is possible to reproduce synchronized picture, audio and the like by decoding the transport stream as shown in FIG. 7 with reference to the header information and management data in the order of arrival.
An apparatus for recording such a transport stream onto a magnetic tape is disclosed in Japanese Laid-Open Publication No. 8-273305. The transport stream cannot be recorded on an analog video tape recorder and the like.
Therefore, the aforementioned publication proposes a method for recording on the magnetic tape an input transport stream or a stream corresponding to a single channel that is selected from the transport stream.
Problems
However, the prior art has the following problems.
The aforementioned method directly records an input transport stream or a stream corresponding to a single channel that is selected from the transport stream. Since a magnetic tape generally has a very large capacity, long recording time can be ensured even if the stream is thus directly recorded thereon.
However, a recording medium having a smaller capacity than that of the magnetic tape, e.g., an optical disk, has very short recording time when the stream is recorded thereon by the aforementioned method, causing a practical problem. For example, a typical high-capacity recording optical disk, DVD-RAM, has a capacity of 2.6 GB. A stream having a bit rate of 6 Mbps can be recorded on the DVD-RAM at most only for about one hour.
On the other hand, in a current analog VTR, recording for two to three hours is possible even in the standard mode. A movie, a sports program and the like normally last for about two hours. In view of the above, a recording optical disk such as DVD-RAM may not be utilized very much as a broadcast recording medium when a stream is recorded thereon using the conventional method.